FIGS. 5(a)-5(e) are sectional views showing an example of a wiring forming method used in the conventional manufacturing method of a semiconductor device, and FIGS. 6(a)-6(f) are sectional views showing a photolithographic process in the wiring forming method. A semiconductor substrate 1 may comprise any material, such as Si or GaAs, if it is normally used in a semiconductor device. A metal film 2a is formed on the semiconductor substrate 1. A metal wiring 2 (referred to as a wiring hereinafter) with a predetermined pattern is formed by patterning the metal film. A resist mask 3a is used in patterning of the metal film 2a.
In addition, a liquid resist 3a is dropped on the metal film 2a on the semiconductor substrate 1. A liquid resist 3b is spread over the entire surface of the metal film 2a. A resist film 3c is formed by baking the liquid resist in heat treatment. A resist film 3d is formed by exposure of the resist film 3c. A resist mask 3 with a predetermined pattern is formed by developing the exposed resist film 3d with developing solution 13.
FIGS. 7, 8(a)-8(c), 9, 10, 11, and 12 are schematic views showing structures of several processing apparatus, such as a sputtering apparatus or a resist applying apparatus, used in steps of the wiring forming method.
As shown in FIG. 7, a sputtering apparatus 210 comprises a substrate table 211 on which the semiconductor substrate 1 is set, a sputtering source 213 generating sputtering particles 213a toward the surface of the semiconductor substrate 1, and an electron gun 212 emitting, for example, electrons toward the sputtering source 213.
As shown in FIG. 8(a), a resist applying apparatus 220 comprises a wafer carried-in portion 220a located on one end of the apparatus body, a resist applying portion 220b located in the center of the apparatus body, and a baking portion 220c located on the other end of the apparatus body.
As shown in FIG. 8(b), a rotating table 221b on which the semiconductor substrate 1 is set is located at the resist applying portion 220b. Above the rotating table 221b, there is located a nozzle 222b for dropping the liquid resist 3a onto the semiconductor substrate 1 on the rotating table 221b. As shown in FIG. 8(c), at the baking portion 220c, there is provided a heating table 221c for heating the semiconductor substrate 1 disposed thereon. In the resist applying apparatus 220, the semiconductor substrate 1 disposed on the wafer carried-in portion 220a is automatically transported to the resist applying portion 220b and to the baking portion 220c.
A resist exposing apparatus 230 comprises, as shown in FIG. 9, a moving table 234 capable of moving in the vertical and horizontal directions, on which the semiconductor substrate 1 is disposed, a converting lens 233 and an exposure light source 231 located above the moving table 234, and a transfer mask 232 disposed between the converting lens 233 and the exposure light source 231. In this structure, a predetermined exposure pattern can be transferred to the semiconductor substrate 1 on the moving table 234.
A developing apparatus 240 comprises, as shown in FIG. 10, a rotating table 241 for rotating the semiconductor substrate 1 disposed thereon. Above the rotating table 241, there are located a developing solution dropping nozzle 242 for dropping a developing solution onto the semiconductor substrate 1 on the rotating table 241 and a wash water blowing nozzle 243 for blowing wash water onto the semiconductor substrate 1 on the rotating table 241.
An ion milling apparatus 250 includes, as shown in FIG. 11, a vacuum chamber 251 having a gas inlet 251a for introducing a gas, such as argon gas, into the chamber and a gas outlet 251b for evacuating the vacuum chamber 251. The vacuum chamber 251 contains a substrate table 254 on which the semiconductor substrate 1 is disposed. A coil 252 for confining plasma 255 is disposed on the side of the gas inlet 251a of the vacuum chamber 251. An accelerating electrode 253 for accelerating ions is disposed at the plasma confined region opposite the substrate table 254.
An oxygen plasma ashing apparatus 260 includes, as shown in FIG. 12, a vacuum chamber 261 having a gas inlet 261a for introducing oxygen gas into the chamber and a gas outlet 261b for evacuating the chamber 261. The chamber 261 contains a substrate table 264 on which the semiconductor substrate 1 is disposed. High frequency applying electrodes 262 for applying high frequency power to the oxygen gas introduced into the chamber 261 are disposed above the substrate table 254 and connected to a high-frequency power supply 263.
The wiring manufacturing method will be described.
First, as shown in FIG. 5(a), the semiconductor substrate 1 is disposed on the substrate table 211 of the sputtering apparatus 210 shown in FIG. 7. After a predetermined gas atmosphere is produced in the apparatus, the sputtering source 213 is irradiated with electrons from the electron gun 212, whereby sputtering particles 213a come out of the sputtering source 213. As shown in FIG. 5(b), the particles are deposited on the semiconductor substrate 1 to form the metal film 2. In this embodiment, a 500 .ANG. thick Ti film and a 1 .mu.m thick Au film are successively formed.
Then, as shown in FIG. 5(c), the resist mask 3 is formed on the metal film 2. More specifically, when the semiconductor substrate 1 with the metal film 2 is carried in the wafer carried-in portion 220a of the resist applying apparatus 220 shown in FIG. 8, it is automatically transported to the resist applying portion 220b. Then, as shown in FIG. 6(a), when the semiconductor substrate 1 is positioned on the rotating table 221b of the resist applying portion 220b, the liquid resist 3a is dropped from the nozzle 222b onto the metal film 2 of the semiconductor substrate 1. Then, as shown in FIGS. 6(b) and 6(c), the rotating table 221b is rotated to spread the liquid resist 3a over the entire surface of the metal film 2 on the semiconductor substrate 1, and the liquid resist 3b is formed.
When the resist is completely applied, the semiconductor substrate 1 is automatically transported to the baking portion 220c. Then, as shown in FIG. 6(d), when the substrate 1 is positioned on the heating table 221c and heated, the liquid resist 3b spread on the entire surface of the metal film 2 is baked, whereby the solid-state resist film 3c is formed.
Thereafter, the semiconductor substrate 1 is transferred to the exposing apparatus 230 shown in FIG. 9 and disposed on the moving table 234 therein. Then, as shown in FIG. 6(e), a predetermined exposure pattern is transferred to the resist film 3c using the transfer mask 232 having the predetermined pattern.
Then, the semiconductor substrate 1 is moved to the developing apparatus 240 shown in FIG. 10. In the apparatus 240, the exposed resist film 3d is developed. More specifically, as shown in FIG. 6(f), the developing solution is dropped from the nozzle 242 onto the resist film 3d on the semiconductor substrate 1 that is disposed on the rotating table 241 of the developing apparatus 240, and it is spread over the entire surface of the resist film 3d by rotation of the rotating table 241, whereby the resist film 3d is developed and the resist mask 3 with the predetermined pattern is formed. Thereafter, the wash water is sprayed from the nozzle 243 onto the surface of the semiconductor substrate 1 to wash away the developing solution. Thus, the developing operation is finished.
Then, referring to FIG. 5(d), the metal film 2 on the semiconductor substrate 1 is patterned by the ion milling apparatus 250 shown in FIG. 11. In the ion milling apparatus 250, ions extracted from the plasma confined region by the accelerating electrode 253 collide with the semiconductor substrate 1 disposed on the substrate table 254, whereby the metal film 2 on the semiconductor substrate 1 is selectively etched.
Finally, the resist mask 3 is removed by the oxygen plasma ashing apparatus 260 shown in FIG. 12. In the ashing apparatus 260, an oxygen gas plasma is applied to the semiconductor substrate 1 disposed on the substrate table 264 in the chamber 260a, whereby the resist mask 3 on the substrate is oxidized and removed.
Thus, according to the conventional wiring forming method in the manufacturing method of a semiconductor device, many substrate processing steps, i.e., steps of sputtering the metal film, applying the resist, transferring the pattern, selectively etching the metal film, and removing the resist, are necessary, and these steps require lots of processing time and very expensive apparatus. In addition, the mask used when the wiring pattern is transferred to the resist is indispensable. Consequently, as described above, the wiring forming process in the manufacturing method of the semiconductor device is an obstacle to reduction of manufacturing costs of the semiconductor device.
Meanwhile, according to Japanese Published Patent Application No. 63-116443, there is disclosed a method of forming a metal film with a predetermined pattern by focused ion beam (FIB) assisted CVD, more specifically, by blowing an organic metal gas, such as hexacarbonyl metal gas, onto a substrate while irradiating the substrate with focused ion beams. The metal film formed by the FIB assisted CVD, however, contains carbon, a constituent of the organic metal gas. Therefore, the resistivity of the metal film is 5 to 10 times higher than the metal contained in the organic metal gas. Additionally, since the depositing speed of the film is extremely low, a film can not be made thick when considering throughput. Consequently, resistivity of the wiring formed from the metal film is significantly high.